Center-distance soft multifocal contact lenses have been shown to slow the progression of myopia,1-5 but practitioners around the world are concerned about the vision produced by soft multifocal contact lens wear in children. Many doctors place soft multifocal contact lenses with center-distance design on children’s eyes and measure the vision. If the child can only read 20/30 to 20/40, the eye care practitioner immediately eliminates soft multifocal contact lenses as a potential treatment or substantially decreases the add power of the contact lens. Based on information from some, 6, 7 but not all,8 orthokeratology myopia control studies, greater peripheral myopic defocus based on baseline refractive error, results in better myopia control. Likewise, stronger add powers result in greater myopic defocus,9, 10 which, in theory, leads to better myopia control. If this is proven to be true, the strongest tolerable add power should be used to maximize myopia control.
Katherine Bickle compared the subjective and objective vision of children who wore single vision, +2.00 D add, +3.00 D add, and +4.00 D add soft contact lenses, each for one week, in randomized order. High contrast distance and near visual acuity were similar when children wore the single vision and multifocal contact lenses, and, on average, it was 20/20 or better with each lens. Low contrast visual acuity was significantly reduced with +3.00 D add and +4.00 D add compared to the single vision and +2.00 D add. Add powers in the extended range may result in some objective vision decrement, but there is no difference between the +2.00 D add and single vision contact lens wear. Children reported more glare or starbursts with the +4.00 D add than +2.00 D add and single vision, more difficulty changing focus from near to distance and back with +3.00 D add and +4.00 D add than +2.00 D add and single vision, and poorer overall vision with the +3.00 D add than the +2.00 D add and single vision contact lenses. However, there were no differences in distance or near vision, ghost images, computer vision, eye strain or tiredness, contact lens comfort, or sporting activities. In summary, +2.00 D add powers do not provide any subjective or objective differences in vision from single vision contact lenses, but stronger add powers occasionally result in slightly poorer vision that may translate to subjective differences in some areas.11 Therefore, eye care practitioners should consider a +2.50 D add power in order to maximize myopia control while providing clear vision.
Vision-specific quality of life was compared between pediatric soft multifocal and soft single vision contact lens wearers using the Pediatric Refractive Error Profile (PREP) Survey.12 Children wearing Proclear Multifocal D (CooperVision, City, ST) contact lenses with a +2.00 D add were compared to a historical control group of age- and gender-matched children wearing 1 Day Acuvue contact lenses (Johnson & Johnson Vision Care, Jacksonville, FL). The change in quality of life from wearing habitual spectacles to wearing contact lenses for one month was compared between the two contact lens modalities. All areas measured (overall vision, near vision, far vision, satisfaction, activities, etc.) improved similarly from spectacle to contact lens wear for the single vision and soft multifocal contact lens wearers, so the multifocal contact lenses do not interfere with daily activities or quality of life for young children.
The Bifocal Lenses In Nearsighted Kids (BLINK) Study, a randomized clinical trial to compare myopia progression while wearing soft bifocal and single vision contact lenses, enrolled 294 children between the ages of 7 and 11 years. In order to be enrolled in the study, all children had to exhibit 20/25 or better binocular distance visual acuity with a +2.50 D add in Biofinity Multifocal “D” contact lenses. The vertexed spherical equivalent distance power with a +2.50 D add was placed on each eye of the children, and an over-refraction was performed to obtain the best visual acuity in each eye. Most children required approximately –0.50 D over-refraction on each eye in order to optimize vision.
The result of the over-refraction was incorporated in the distance power and dispensed to the subjects. During the follow-up visit, most over-refractions were plano and almost every subject was able to read the 20/25 line or better with +2.50 D add soft multifocal contact lenses with a center-distance design, as long as the over-refraction was incorporated in the distance power of the contact lens.
Rarely will a child continue to complain of poor vision after incorporating the over-refraction in the distance power of the contact lens. If that happens, the doctor should consider reducing the add power by only one step to see if that improves vision (see Table). To date, only one child has required a reduction in add power to optimize vision. In summary, soft multifocal contact lenses with a +2.50 D add power provide myopia control and clear vision. In order to optimize vision, a spherical over-refraction must be performed, and the distance power of the contact lens must be adjusted. Rarely do children require lower add powers to optimize vision.
Adjusting multifocal contact lenses to optimize vision for myopia control
- Place the distance power with a +2.50 D add that matches the spherical equivalent, vertexed power of the manifest refraction on the eye.
- Perform an over-refraction, and expect an extra –0.50 to –0.75 D more minus to optimize vision.
- Place the new distance power, incorporating the over-refraction, with a +2.50 D add on the eye.
- Lower the add power one step, only if the child complains of poor vision or exhibits worse than 20/25 visual acuity (this is very rare).
Jeff Walline is Associate Dean for Research and Graduate Education at the Ohio State University College of Optometry. He has published nearly 200 papers, abstracts and book chapters, is a world authority on pediatric contact lens wear and myopia control, and can’t recommend In-N-Out Burger to you highly enough.